985
FXUS65 KBYZ 161843
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
1243 PM MDT WED SEP 16 2026
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THURSDAY
AFTERNOON AND EVENING. LOCALLY HEAVY RAIN POSSIBLE OVER SE
MONTANA WITH ANY SHOWERS/THUNDERSTORMS.
- A FEW STRONG THUNDERSTORMS ARE POSSIBLE FROM BILLINGS EAST
FRIDAY AFTERNOON INTO THE EVENING HOURS.
- STRONG PRECIPITATION CHANCES SPREAD ACROSS THE AREA FROM FRIDAY
AFTERNOON THROUGH THE WEEKEND, WITH THE POTENTIAL FOR LOCALLY
HEAVY RAINFALL WIDESPREAD THROUGH SATURDAY NIGHT.
- CHANCES FOR WIDESPREAD WEEKEND PRECIPITATION ACCUMULATIONS OF
MORE THAN A HALF AN INCH SITS AT 80+% FOR MOST AREAS, WITH
CHANCES FOR MORE THAN AN INCH SHOWING 60-70% PROBABILITIES.
DISCUSSION
REST OF TODAY THROUGH NEXT TUESDAY...
WEAK RIDGING OVER THE AREA TODAY KEEPING QUIET AND MOSTLY SUNNY
CONDITIONS OVER THE AREA THIS AFTERNOON. A DISTURBANCE CROSSING S.
CANADA JUST NORTH OF THE MONTANA BORDER IS PUSHING A WEAK
NORTHERLY WIND SHIFT THROUGH THE AREA AT THIS TIME, WITH A
REINFORCEMENT OF THE COOLER AIR WE HAVE SEEN OVER THE PAST FEW
DAYS. GENERALLY LIGHT WINDS TONIGHT MAY ALLOW PATCHY FOG TO
DEVELOP OVER RIVER VALLEYS TONIGHT, MAINLY EAST OF BILLINGS.
OTHERWISE A QUIET AND SEASONALLY COOL NIGHT ANTICIPATED ACROSS THE
REGION.
LOW LEVEL WINDS TURN SOUTHEASTERLY TOMORROW AND WORK TO ADVECT IN
PLAINS MOISTURE TO THE AREA THROUGH THE DAY. AT THE SAME TIME A
DEEPENING UPPER LOW OVER NORCAL WILL DRIFT THIS DIRECTION, WITH
ENERGY ROTATING AROUND THE EASTERN SIDE OF THE LOW PUSHING UP INTO
OUR AREA BY MID AFTERNOON. THIS ENERGY WILL BE ENOUGH FOR ISOLATED
TO SCATTERED SHOWERS AND A FEW THUNDERSTORMS TO DEVELOP OVER
SOUTHERN ZONES DURING THE AFTERNOON HOURS. WILL HAVE TO KEEP AN
EYE ON CONVECTION OVER SE MONTANA THROUGH THURSDAY EVENING WHERE
THE STRONGEST MOISTURE ADVECTION ARRIVES DURING THIS PERIOD WITH A FEW
MODELS SHOWING LOCALLY HEAVY RAINFALL NOT TOO FAR AWAY FROM
CARTER/FALLON COUNTIES. PWAT VALUES CLIMB TO 200% OF NORMAL
THURSDAY NIGHT.
THERE MAY BE A FEW SHOWERS LINGERING OVERNIGHT INTO FRIDAY
MORNING, BUT OVERALL THIS PERIOD LOOKS TO BE A BREAK BEFORE
STRONGER FORCING AND MORE WIDESPREAD PRECIPITATION DEVELOPS FOR
FRIDAY AFTERNOON THROUGH SATURDAY NIGHT. THERE IS A PERIOD FRIDAY
AFTERNOON INTO FRIDAY EVENING WHERE SHEAR AND CAPE PROFILES
COMBINE TO PROVIDE THE POTENTIAL FOR A FEW STRONG TO POSSIBLY
SEVERE THUNDERSTORMS. MODELS ARE NOT IN GREAT AGREEMENT WITH
EXACTLY WHERE THE HIGHEST POTENTIAL FOR STRONG STORMS WILL BE, BUT
AREAS JUST EAST OF BILLINGS SEEM TO BE THE AREA MODELS WANT TO GET
STORMS GOING EARLY TO MID AFTERNOON, SLOWLY SPREADING EASTWARD
THROUGH MID EVENING. AI/ML GUIDANCE HAS A 5 TO 15 PERCENT SEVERE
THREAT OVER THIS AREA. SPC WILL LIKELY WAIT TO SEE A BETTER MODEL
CONSENSUS AS THE HI-RES CAM MODELS START TO ADVERTISE THIS PERIOD
BEFORE ADJUSTING THE GENERAL THUNDERSTORM OUTLOOK UPWARD. SO, IF
YOU HAVE OUTDOOR PLANS FRIDAY AFTERNOON, BE PREPARED FOR
THUNDERSTORM ACTIVITY, WITH A FEW STRONG STORMS (HAIL/STRONG
WINDS/VERY HEAVY RAINFALL) POSSIBLE.
PRECIPITABLE WATER VALUES REACH 200-225% OF NORMAL FRIDAY
AFTERNOON THROUGH SATURDAY ACROSS THE ENTIRE FORECAST AREA. THIS
MOISTURE WILL PRESENT THE POTENTIAL FOR LOCALLY HEAVY RAINFALL
DURING THIS PERIOD. LATEST MODEL RUNS CONTINUE TO MOVE THE SLOW
MOVING NORCAL LOW IN A FAVORABLE TRACK FOR A WIDESPREAD LONG
DURATION PRECIPITATION EVENT OVER THE AREA. 13Z NBM IS SHOWING
PROBABILITIES FOR HALF AN INCH OR MORE PRECIPITATION ACCUMULATION
AT ABOVE 80% FOR MOST OF THE AREA FROM FRIDAY AFTERNOON THROUGH
SUNDAY MORNING. PROBABILITIES FOR AN INCH OR MORE ARE ABOVE 60%
FOR MOST OF THE AREA. THESE HIGH PROBABILITIES ARE DUE TO BOTH THE
ECMWF AND GFS ENSEMBLES SHOWING VERY SIMILAR STORM TRACKS AND
MOISTURE PROFILES FOR THIS WEEKEND. THAT GOOD AGREEMENT IS DRIVING
THE HIGH NBM PROBABILITIES, ALONG WITH THE UNUSUALLY HIGH
ATMOSPHERIC MOISTURE LEVELS OVER THE REGION. WPC HAS A MARGINAL
RISK FOR EXCESSIVE RAINFALL OVER THE AREA BOTH FRIDAY AND SATURDAY
NOW. SO, PLAN ON A WET WEEKEND, ESPECIALLY SATURDAY, IF YOU HAVE
OUTDOOR PLANS AND AVE A WAY TO GET WEATHER ALERTS IN CASE FLOOD
ADVISORIES OR WARNINGS BECOME NECESSARY.
GFS ENSEMBLE GRABS THE UPPER LOW AND QUICKLY SHIFTS IT EAST OF
THE AREA ON SUNDAY, ENDING PRECIPITATION CHANCES FOR ALL BUT THE
FAR EASTERN ZONES BY EARLY AFTERNOON. ECMWF ENSEMBLE IS SLOWER
WITH THIS PROGRESSION AND LINGERS MORE WIDESPREAD PRECIPITATION
CHANCES INTO MONDAY MORNING, BEFORE PUSHING EAST OF THE AREA
MONDAY AFTERNOON. NBM COMBINES THESE AND DRIES OUT THE WESTERN
FOOTHILLS SUNDAY AFTERNOON, BUT KEEPS CHANCE OR BETTER
PRECIPITATION CHANCES GOING OVER CENTRAL AREAS INTO SUNDAY NIGHT
WITH PRECIPITATION CHANCES FINALLY DRYING UP BY MONDAY AFTERNOON
OVER CARTER/FALLON COUNTIES.
THIS SYSTEM CONTINUES TO LOOK SIGNIFICANTLY WARMER THAN LAST
WEEKENDS SYSTEM. AS SUCH, THE FORECAST FOR SNOW LEVELS REMAINS AT
THE HIGHEST ELEVATIONS OF THE BEARTOOTH/ABSAROKA/CRAZY MOUNTAINS,
WITH FORECAST ACCUMULATIONS THROUGH THE WEEKEND STAYING UNDER 5
INCHES. WILL CONTINUE TO MONITOR THE SNOWFALL SITUATION TO SEE IF
IMPACTS TO THE BEARTOOTH HIGHWAY WOULD NECESSITATE AN ADVISORY,
BUT AT THIS TIME IT DOESN'T APPEAR AN ADVISORY WILL BE NEEDED.
CHAMBERS
AVIATION
18Z TAF AND AVIATION DISCUSSION...CAN'T RULE OUT PATCHY RIVER
VALLEY FOG ACROSS THE AREA AFTER MIDNIGHT TONIGHT. ANY FOG WILL
LINGER THROUGH 15-16Z THURSDAY MORNING WITH LOCAL IFR OR LOWER
CONDITIONS POSSIBLE. OTHERWISE VFR CONDITIONS WILL PREVAIL THROUGH
THURSDAY MORNING. ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS ARE
EXPECTED THURSDAY AFTERNOON OVER THE SOUTHERN TIER OF THE
FORECAST AREA, DRIFTING NORTH INTO THE EVENING HOURS. LOCALLY
HEAVY RAINFALL IS POSSIBLE FOR ANY ACTIVITY OVER SE MONTANA, WITH
BRIEF IFR CONDITIONS NEAR PRECIPITATION AREAS.
NORTH TO NORTHEAST WINDS WILL GUST 10 TO 20 KTS THIS AFTERNOON
INTO EARLY EVENING. WINDS WILL BE GENERALLY LIGHT TONIGHT (KLVM
REVERSE GAP WINDS THE EXCEPTION) WITH A SLOW SHIFT TO THE
SOUTHEAST BY MORNING. SOUTHEAST WIND GUSTS WILL REACH 25 KTS ON
THURSDAY OVER SE MONTANA (KMLS/KBHK), WHILE THE REST OF THE AREA
CONTINUES TO SEE GENERALLY LIGHT SOUTHERLY WINDS. CHAMBERS
PRELIMINARY POINT TEMP/POPS
THU FRI SAT SUN MON TUE WED
-----------------------------------------------------------
BIL 047/077 055/081 056/067 053/073 051/077 051/078 050/077
00/B 14/T +9/T 74/W 10/U 00/U 00/U
LVM 045/079 050/077 048/067 046/074 046/078 047/078 046/078
03/T 38/T 98/T 61/B 00/U 00/U 01/U
HDN 045/081 052/082 053/069 049/073 047/078 047/079 046/080
00/B 13/T +9/T 75/T 20/U 00/U 00/U
MLS 048/081 059/083 057/069 053/071 051/075 051/077 050/078
01/B 12/W 99/T 86/W 31/B 00/U 00/U
4BQ 050/080 059/082 057/071 054/070 052/073 052/076 051/079
02/W 31/B 99/T 88/T 42/W 00/U 00/U
BHK 043/078 053/080 051/068 049/070 047/074 047/076 046/079
01/N 21/B 99/T 87/T 42/W 00/U 00/U
SHR 044/079 050/081 050/068 046/071 045/076 044/077 044/080
03/W 25/T 99/T 87/T 31/U 00/U 01/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page